The present invention relates generally to internal combustion engines, and more particularly to a direct lever overhead valve system for controlling valve opening and closing.
It is known to use V-shaped cam followers in combination with push rods 10 and rocker arms in a valve operating system in an overhead valve engine to thereby control movement of the valves. U.S. Pat. No. 5,357,917 to Everts is one example. However, the Everts device is a complicated combination of components operating between a cam and the valves.
The present invention is directed to a direct lever overhead valve system designed to directly control valve operation based on cam rotation. The direct lever system is particularly adapted to simplify valve operation by translating cam rotation directly to the valve stems.
The direct lever system may utilize a pair of generally L-shaped levers, each with a cam following surface on a first lever arm and a valve-operating surface at a second lever arm. The levers may be nestable and act about a common pivot.
The preferred embodiment of the invention provides an overhead valve engine including a cylinder bore having an outer end; and a crankshaft assembly including a substantially straight crankshaft, a substantially cylindrical journal eccentrically mounted on the crankshaft, a one-piece connecting rod rotatably mounted on the journal, a counterweight mounted on the crankshaft, and a timing gear mounted on the crankshaft. The engine also includes a cam shaft having a cam surface and an axis inward of the outer end of the cylinder bore; two valves having opened and closed positions; two valve stems, each valve stem being attached to a valve; and two generally L-shaped and pivotably mounted valve operating levers, each lever including a first end having a cam follower in contact with the cam surface, a pivot axis about which the lever pivots, and a valve arm in contact with a valve stem, where movement of the lever caused by the cam surface causes the lever to pivot and the valve arm to depress the valve stem and thus open the valve.
The invention also provides a direct lever system for an overhead valve engine, the system including a cylinder bore having an outer end; a cam shaft having a cam lobe and an axis inward of the outer end of the cylinder bore; two valves having opened and closed positions; and two valve stems, each valve stem being attached to a valve. The direct valve system also includes two generally L-shaped and pivotably mounted valve operating levers, each lever including a first lever arm having a cam follower in contact with the cam lobe, a pivot axis about which the lever pivots, and a valve arm in contact with a valve stem, where movement of the lever caused by the cam lobe causes the lever to pivot and the valve arm to depress the valve stem and thus open the valve.
The pivot axes of the levers can be coincidental. Alternatively, the direct lever system may employ a pair of generally L-shaped levers that are not nested and that act on separate but substantially parallel pivots.
The invention also provides a crankshaft assembly for an engine, the assembly including a substantially straight crankshaft; a substantially cylindrical journal eccentrically mounted on the crankshaft; a one-piece connecting rod rotatably mounted on the journal; a counterweight mounted on the crankshaft; and a timing gear mounted on the crankshaft.
The invention also provides a process for manufacturing a connecting rod having a desired connecting rod shape and a desired thickness for an overhead valve engine, the process including extruding a bar of material with a cross section substantially similar to the desired connecting rod shape and including an extruded bore; cutting the bar into substantially equivalent slices of the desired thickness; and finishing at least two bores in each slice.